GATF Reports on Plate Reading Technologies Relevant to CTP Plates
Press release from the issuing company
Pittsburgh, Pa., July 22, 2002 — To help printers select a plate reading system that will work best with a particular brand of plates, the Graphic Arts Technical Foundation (GATF) releases a new study. Plate Reading Technologies and Their Performance on CTP Plates charts the accuracy of five possible solutions for measuring a wide variety of computer-to-plate (CTP) lithographic plates, thus helping printers avoid costly plate remakes and rejected work.
Since the introduction of CTP to the industry, a system capable of measuring dot area accurately on a lithographic printing plate has been needed. In a laboratory environment, technology with this capability has been used for years. However, these systems are very expensive and time consuming for a production environment. Over the past few years the industry has seen the introduction of a few inexpensive portable systems using charge-coupled device (CCD) and complementary metal oxide semiconductor (CMOS) technologies that claim the ±1% accuracy needed for production control and calibration.
GATF sought to determine how accurate these systems truly are at measuring a wide variety of plates, not only at the midtone but also across an entire tone scale. Through the generosity of the several manufacturers, the performance of four CCD plate reading systems were examined: the Acme Plate Reader, Centurfax CC-Dot 4, Viptronic/Beta Screen Ultra Dottie, and the Techkon DMS 910. Additionally the performance of the X-Rite 530 Spectrodensitometer was plotted because a large number of printers reported using the 500 series as a plate reader. All systems were benchmarked against the Jandel planimeter—a system proven accurate but not practical for a production setting.
While not one of the five measurement systems were capable of accurately measuring all 14 plates used for the study, according to the Jandel values, all five systems prove accurate in measuring several plates each. Thus Plate Reading Technologies and Their Performance on CTP Plates helps printers select a plate reading system that is right for their plates. The plates that resulted in the most variation were those with low contrast (dark non-image surface and emulsions) or certain colored emulsions. It appears that some plate readers were unable to determine the difference between plate surface and emulsion which caused the variation in dot area. The plates with the most contrast between the image and non-image area generally gave better results with any of the five plate readers.
Plate Reading Technologies and Their Performance on CTP Plates also reports on whether orientation of the instrument influences the result, discusses how pre-baking and post-baking are important issues when measuring plates, and shows how calibration of a platesetter is very important for controlling the output.
While preliminary results of the study were reported at GATF’s Tech Alert conference in January 2002, the full study is now available in this published form. Plate Reading Technologies and Their Performance on CTP Plates is the latest study in a series of Research and Technology Reports (RTR) published by the Foundation. As an independent, third-party organization, GATF reports are objective and original research studies designed to help printers evaluate technologies on their own by guiding consumers to ask the right questions. Methodology is described in all reports.
With seven appendices of graphs and tables detailing the findings, Plate Reading Technologies and Their Performance on CTP Plates (ISBN 0-88362-426-5) is a 48-page soft cover booklet available for $129 ($59 for GATF/PIA members), not including shipping. Orders may be placed by contacting GATF by phone at 800/662-3916 (U.S. and Canada) or 412/741-5733 (all other countries); fax at 412/741-0609; or online from the GAIN Bookstore. Mail orders to GATF Products, P.O. Box 1020, Sewickley, PA 15143-1020. Indicate Order No. 1627.
Plate Reading Technologies and Their Performance on CTP Plates
by Gregory M. Radencic and John T. Lind
Table of Contents
Plate Reading Technologies...1
Accuracy of the Midtone...3
Accuracy Across the Tone Scale...3
Angle of Orientation for Measurement...4
CCD/CMOS vs. Spectrodensitometer...4
Appendix 1: Plate properties...9
Appendix 2: Measurements of all plates with each plate reading system...11
Appendix 3: Density difference of plate surface and emulsion...19
Appendix 4: CIELAB data of plate emulsion (image area)...21
Appendix 5: CIELAB data of plate surfaces (non-image area)...23
Appendix 6: Tone curves of each plate...25
Appendix 7: Difference from planimeter...33
GATFPress: Selected Titles...44
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